How to modify the Sugar 7 session timeout?

I have used the php default setting, which has session timeout value of 1440 seconds. However, sugar7 session seem never time out. How could I enabled the session timeout?I have modify session.gc_maxlifetime = 7200 but this only for for sugarcrm 6, not for sugarcrm 7.

My SugarCRM version is 7.5I have posted before but still no solution right now.Could anyone help?